I agree with the need for preparations - above all, with what Theymos said about finding clear criteria for a malicious attack.
I'm also a bit concerned about the "new monopolies" that could emerge after a PoW change. It may sound a bit naive, but - is there a possibility to create/fund an open hardware project for mining chips running the "new Bitcoin algorithm"? It's true however that major "chip foundries" are located in China, but there are at least some scattered around the world (mainly Europe and North America) which could step in for production.
I think electricity cost plays a larger role in terms of geographical (and by extension legislative) decentralization than where the miners are produced. If Europe and the US had electricity prices closer to China I'd expect the dominance of a certain ASIC manufacturer to be much less of an issue than it is today.
In this case, time is on our side - renewable-based (e.g. solar/wind powered) off-grid mining probably very soon (in the next 5 years) could be cheaper than Chinese electricity, where the cheapest price is ~3 cent per kWh. I already mentioned in other threads that
~2 cent/kWh solar power costs are probably becoming real in the next 5-10 years (the article I linked makes pretty conservative assumptions).
While China has good solar energy spots, there are even better ones in the Americas (south-western North America and western South America) and, of course, Africa and the Middle East.